1. Field of the Invention
The present invention is concerned with methods for detecting hepatitis C virus (HCV) infection. More particularly, the present invention is concerned with methods for detecting HCV infection and being able to differentiate between individuals having chronic HCV infection and those that have cleared the infection in blood samples that are older than 6 hours. Still more particularly, the present invention is concerned with identifying individuals who have cleared the HCV infection but still continue testing positive for antibody to HCV. Even more particularly, the present invention is concerned with performing an antibody-based assay on a fluid sample, which identifies individuals having antibodies to HCV, determining the optical density of the sample after the addition of the antibodies, and then performing an assay using molecular detection methods on those samples testing positive for antibodies in order to correlate optical density with samples testing positive using an antibody-based assay and using molecular detection methods. Most particularly, the present invention is concerned with performing an antibody-based assay for HCV in a fluid sample, determining the optical density of the sample and then using the optical density to predict the likelihood that sample was taken from an individual with chronic HCV infection.
2. Description of the Prior Art
Hepatitis C is a single stranded RNA virus belonging to the Flaviviridae family of virus. The virus is a principal cause of liver disease in the United States. Infection is detected by serology testing for antibody produced in response to the virus. Serology provides an inexpensive method for screening the population but this type of testing detects two groups of individuals. The first group includes individuals that were infected and recovered from the infection. The second group includes chronically infected individuals. But, the antibody test cannot differentiate between the two groups. Chronic infection occurs in 75% to 85% of infected individuals. Therefore, 15% to 25% of individuals that test positive for antibody to HCV have actually cleared the infection and are themselves not infectious. In order to overcome this deficiency, new molecular detection methods are replacing serology as the method of choice for detection of the virus. However, molecular detection methods are costly in comparison to antibody-based methods and therefore, such methods are recommended only for samples first testing positive in an antibody-based assay. In some applications the prohibitive cost of testing may be overcome by the pooling of multiple samples before molecular testing. Accordingly what is needed is a method of determining chronic HCV infection which does not require expensive molecular detection methods. What is further needed are methods of predicting which individuals have chronic HCV infection and which individuals have cleared the infection without resorting to molecular detection methods.